On Thu, 5 May 2022 at 05:06, Rob Clark <robdclark@xxxxxxxxx> wrote:
>
> On Wed, May 4, 2022 at 6:55 PM Jessica Zhang <quic_jesszhan@xxxxxxxxxxx> wrote:
> >
> > mdp5_get_global_state runs the risk of hitting a -EDEADLK when acquiring
> > the modeset lock, but currently mdp5_pipe_release doesn't check for if
> > an error is returned. Because of this, there is a possibility of
> > mdp5_pipe_release hitting a NULL dereference error.
> >
> > To avoid this, let's have mdp5_pipe_release check if
> > mdp5_get_global_state returns an error and propogate that error.
> >
> > Changes since v1:
> > - Separated declaration and initialization of *new_state to avoid
> > compiler warning
> > - Fixed some spelling mistakes in commit message
> >
>
> Note that mdp5_mixer_release() needs the same treatment.. one more comment below
>
> > Signed-off-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c | 15 +++++++++++----
> > drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h | 2 +-
> > drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c | 20 ++++++++++++++++----
> > 3 files changed, 28 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c
> > index ba6695963aa6..97887a2be082 100644
> > --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c
> > +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c
> > @@ -119,18 +119,23 @@ int mdp5_pipe_assign(struct drm_atomic_state *s, struct drm_plane *plane,
> > return 0;
> > }
> >
> > -void mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe)
> > +int mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe)
> > {
> > struct msm_drm_private *priv = s->dev->dev_private;
> > struct mdp5_kms *mdp5_kms = to_mdp5_kms(to_mdp_kms(priv->kms));
> > struct mdp5_global_state *state = mdp5_get_global_state(s);
> > - struct mdp5_hw_pipe_state *new_state = &state->hwpipe;
> > + struct mdp5_hw_pipe_state *new_state;
> >
> > if (!hwpipe)
> > - return;
> > + return -EINVAL;
>
> At least per the current code, !hwpipe is "normal".. I think that fits
> the model of things like kfree(NULL), so lets make this just return 0
Especially since we release the r_hwpipe w/o additional check. And
r_hwpipe frequently is NULL.
>
> > +
> > + if (IS_ERR(state))
> > + return PTR_ERR(state);
> > +
> > + new_state = &state->hwpipe;
> >
> > if (WARN_ON(!new_state->hwpipe_to_plane[hwpipe->idx]))
> > - return;
> > + return -EINVAL;
> >
> > DBG("%s: release from plane %s", hwpipe->name,
> > new_state->hwpipe_to_plane[hwpipe->idx]->name);
> > @@ -141,6 +146,8 @@ void mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe)
> > }
> >
> > new_state->hwpipe_to_plane[hwpipe->idx] = NULL;
> > +
> > + return 0;
> > }
> >
> > void mdp5_pipe_destroy(struct mdp5_hw_pipe *hwpipe)
> > diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h b/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h
> > index 9b26d0761bd4..cca67938cab2 100644
> > --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h
> > +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h
> > @@ -37,7 +37,7 @@ int mdp5_pipe_assign(struct drm_atomic_state *s, struct drm_plane *plane,
> > uint32_t caps, uint32_t blkcfg,
> > struct mdp5_hw_pipe **hwpipe,
> > struct mdp5_hw_pipe **r_hwpipe);
> > -void mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe);
> > +int mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe);
> >
> > struct mdp5_hw_pipe *mdp5_pipe_init(enum mdp5_pipe pipe,
> > uint32_t reg_offset, uint32_t caps);
> > diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c
> > index 228b22830970..979458482841 100644
> > --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c
> > +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c
> > @@ -311,12 +311,24 @@ static int mdp5_plane_atomic_check_with_state(struct drm_crtc_state *crtc_state,
> > mdp5_state->r_hwpipe = NULL;
> >
> >
> > - mdp5_pipe_release(state->state, old_hwpipe);
> > - mdp5_pipe_release(state->state, old_right_hwpipe);
> > + ret = mdp5_pipe_release(state->state, old_hwpipe);
> > + if (ret)
> > + return ret;
> > +
> > + ret = mdp5_pipe_release(state->state, old_right_hwpipe);
> > + if (ret)
> > + return ret;
> > +
> > }
> > } else {
> > - mdp5_pipe_release(state->state, mdp5_state->hwpipe);
> > - mdp5_pipe_release(state->state, mdp5_state->r_hwpipe);
> > + ret = mdp5_pipe_release(state->state, mdp5_state->hwpipe);
> > + if (ret)
> > + return ret;
> > +
> > + ret = mdp5_pipe_release(state->state, mdp5_state->r_hwpipe);
> > + if (ret)
> > + return ret;
> > +
> > mdp5_state->hwpipe = mdp5_state->r_hwpipe = NULL;
> > }
> >
> > --
> > 2.35.1
> >
--
With best wishes
Dmitry
